Differentiation from I vs. J
The type set of the Gothic print typeface usually has only one grapheme for today's majuscules I and J. In the transcription, this grapheme is not represented according to the phonetic value as an I- or J-grapheme, but rather the majuscule J.
In the case of abbreviations, the majuscule J is also used generally (e. g. J. E. Hitzig for Julius/Iulius Eduard Hitzig and K. J. Beck for Karl Isidor/Jsidor Beck).